Traditional vehicle navigation systems have typically included a processing device (CPU) that controls the navigation functions, a storage device (e.g., hard drive, CD-ROM, DVD-ROM) for storing map data, a global positioning system (GPS) receiver for locating the position of the vehicle, a display device (e.g., LCD screen) for displaying the location of the vehicle and a calculated route, a speaker, and various sensors for detecting vehicle direction and vehicle speed. In use, the CPU uses the vehicle location, the coordinates of a desired destination, and stored map data, to calculate a route of travel.
Satellite-based or radio-based (broadcast) traffic information may also be used in calculating a route. The location of the vehicle is then shown superimposed over a map image on the display device along with the calculated path of travel, and movement of the vehicle is reflected as a change of position of the vehicle on the map image, which is updated as movement of the vehicle progresses.
One downside to traditional onboard vehicle navigation systems is the relatively high cost typically associated therewith. Consequently, less complex and lower cost vehicle navigation systems have recently gained interest. In these systems, many of the functions typically performed by the onboard navigation system are performed off-board (remotely), such as by a server located at a central station (i.e., information processing/distribution center). More specifically, the central station may be equipped with a database of map data and any other technology necessary to receive a route calculation request from a vehicle, to calculate a route, and to transmit the calculated route to the vehicle. In this manner, the vehicle need only be capable of sending location and destination information to the central station and of receiving route guidance information from the central station. The cost to the purchaser of a vehicle of such a server-based navigation system may thus be greatly reduced in comparison to the cost of a traditional onboard vehicle navigation system.
While many of the traditional navigation system components may be removed from a vehicle in such a server-based vehicle navigation system, a means of communication between the vehicle and the central station must still be provided. It is being increasingly suggested that these communications occur via a mobile communication device (e.g., a mobile phone), which may be connected to the central station via the Internet, etc., and to a vehicle by a wired or wireless link (e.g., Bluetooth®). The mobile phone may be provided with particular software that allows or enhances its ability to function in this manner. Consequently, it is possible to use a mobile phone as a communications conduit between a vehicle and a remotely located central station, to display map and route guidance information received from the central station via the mobile phone on a display device located in the vehicle, and to broadcast audible route guidance and/or other associated navigation communications over a vehicle's speaker system.
One problem with using a mobile phone as a primary navigation data communications conduit between a vehicle and a remotely located central station is that the amount of navigation data that must be exchanged between the central station and the vehicle is typically quite large. This is problematic for multiple reasons. First, the time required to download the necessary navigation data and to periodically update the navigation data may be significant, which might result in guidance problems. Second, many if not most mobile phone usage plans place a limit on the amount of data that may be transmitted within a given time period without incurring additional fees. Consequently, because of the large amount of navigation data that must typically be transferred in such a server-based vehicle navigation system, the use of a mobile phone as a communications conduit may result in significant data transfer overage fees.
To this end, a number of modifications have been proposed with respect to minimizing the amount of data that must be transferred when using a server-based vehicle navigation system. These modifications have generally focused on minimizing the amount of map and/or basic route information that must be transmitted between a central station and a vehicle, such as by limiting the data sent to data related only to a geographic area in close proximity to the current location of the vehicle.
In the case of a traditional vehicle navigation system or a server-based vehicle navigation system, delivering traffic information to a vehicle may be beneficial for a number of reasons including, for example, because such information may be used to determine or alter a route traveled by the vehicle. While basic traffic information, alerts, etc., may simply be broadcast over one or more radio frequencies for receipt and use by a vehicle operator, traffic information may also be utilized by vehicle navigation systems to enhance route calculation in a manner that avoids delays resulting from traffic problems (accidents, congestion, construction, etc.).
For use in electronic navigation, traffic information must be gathered and provided to a vehicle's navigation system. Traffic information available to onboard vehicle navigation systems has typically been transmitted via satellite or within FM radio signals—i.e., via radio data system (RDS) or radio broadcast data system (RBDS) signals. In another system, one or a plurality of (probe) vehicles equipped with on-board navigation and a telecommunications unit (e.g., an embedded phone) may transmit to a remote server various data relating to the travel of the vehicle. This data may include, for example, the location, speed and route of the vehicle. As the vehicle periodically transmits this data to the remote server, the server can use the vehicle's location, the time required for the vehicle to travel from one reporting point to the next, and the known speed limit for the route traveled by the vehicle, to determine whether there is a traffic problem in the area of the vehicle.
Traffic information may also be provided to vehicle navigation systems over mobile networks, so that a mobile communication device (e.g., mobile phone) carried by a vehicle operator may be accessed to view traffic information or may be used to provide traffic information to a vehicle navigation system. Traffic information provided in this manner may differ from the traffic information provided by traditional satellite or broadcast traffic information. For example, as the remote server described above receives more information from the various probe vehicles in a given area, the server may aggregate the data, make a conclusion about traffic conditions and, if appropriate, send back via the telecommunications units thereof, updated route guidance instructions to the same vehicles from which the data was received. Additionally, such a system may also send the same updated route guidance information to other vehicles in the area that are not equipped with an onboard telecommunications unit by making use of a non-embedded mobile communication device, such as an occupant's mobile phone. Because traffic information transmitted in this manner may be updated more frequently (is newer) than traffic information obtained from a broadcast signal, this information can be advantageous to most accurately calculating a navigation route that bypasses traffic problems.
Whether a mobile communication device such as a mobile phone is used to deliver traffic-based navigation information to a traditional vehicle navigation system or is part of a server-based vehicle navigation system, the aforementioned problems associated with data transfer rates, data transfer limitations, and excess usage fees, still exist. While consideration has been given to reducing the amount of general map or route data that must be transferred by a mobile phone in a server-based vehicle navigation system, no such consideration appears to have been given to the transmission of navigation data updates resulting from changes in traffic conditions. That is, when route calculation and guidance is based at least in part on traffic conditions, no consideration has been given to reducing the more frequent updating of calculated route data that will typically be required to accurately avoid traffic problems.
There is thus a need for a system and method whereby the amount of navigation data transmitted by a server-based vehicle navigation system as a result of changing traffic conditions may be minimized. Systems and methods of the present invention satisfy this need.